The present invention relates to a nonmagnetic material particle-dispersed ferromagnetic material sputtering target for use in the deposition of a magnetic thin film of a magnetic recording medium, and particularly of a granular magnetic recording film of a hard disk adopting the perpendicular magnetic recording system, and to a sputtering target with a leakage magnetic flux which is able to obtain stable electrical discharge when sputtered with a magnetron sputtering device, and which has high density and generates few particles during sputtering.
In the field of magnetic recording, technology has been developed for improving the magnetic property by uniformly micro-dispersing nonmagnetic materials in a magnetic thin film. As one example thereof, with a hard disk recording medium adopting the perpendicular magnetic recording system, a granular film is adopted for blocking or weakening the magnetic interaction between magnetic particles in the magnetic recording film by using a nonmagnetic material, and improving the various properties as a magnetic recording medium.
Co—Cr—Pt—SiO2 is known as one of the optimal materials for the foregoing granular film, and the granular film of Co—Cr—Pt—SiO2 is generally produced by sputtering a nonmagnetic material particle-dispersed ferromagnetic material target in which SiO2 as the nonmagnetic material is uniformly micro-dispersed in the ferromagnetic Co—Cr—Pt alloy base material having Co as its main component.
It is widely known that this kind of nonmagnetic material particle-dispersed ferromagnetic material sputtering target is produced with the powder metallurgy method since the nonmagnetic material particles cannot be uniformly micro-dispersed in the ferromagnetic alloy base material with the dissolution method.
For example, proposed is a method of performing mechanical alloying to alloy powder with an alloy phase produced with the rapid solidification method and powder configuring a ceramic phase, uniformly dispersing the powder configuring the ceramic phase in the alloy powder, and molding this by way of hot press to obtain a sputtering target for a magnetic recording medium (Patent Document 1).
Another way of preparing a nonmagnetic material particle-dispersed ferromagnetic material sputtering target is to use commercially available raw material powders for the respective components configuring the target, even without the alloy powder produced with the rapid solidification method. The raw material powders are weighed to the intended composition, mixed with well-known methods by using a ball mill or the like, and molding and sintering the mixed powder by hot press.
If a high density material can be obtained after sintering, it is generally known that the generation of particles, which becomes problematic during the sputtering, can be reduced.
There are various types of sputtering devices, but a magnetron sputtering device is broadly used in light of its high productivity for the deposition of the foregoing magnetic recording film.
This sputtering method makes a positive electrode substrate and a negative electrode target face each other, and generates an electric field by applying high voltage between the substrate and the target under an inert gas atmosphere.
Here, the sputtering method employs a fundamental principle where inert gas is ionized, plasma composed of electrons and positive ions is formed, and the positive ions in this plasma collide with the target (negative electrode) surface so as to discharge the atoms configuring the target. The extruded atoms adhere to the opposing substrate surface, wherein the film is formed. As a result of performing the sequential process described above, the material configuring the target is deposited on the substrate.
The magnetron sputtering device is characterized in comprising a magnet on the back side of the target, and the magnetic flux (leakage magnetic flux) leaked from the magnet onto the target surface causes the electrons to engage in cycloidal motion in the vicinity of the target surface, whereby plasma is generated efficiently.
[Patent Document 1] Japanese Published Unexamined Patent Application No. H10-88333